U.S. patent application number 11/051700 was filed with the patent office on 2005-09-08 for radiation curable aqueous binders for ink jet inks.
Invention is credited to Graziano, Louis Christopher, Lein, George Max, Wu, Richard Shu-Hua.
Application Number | 20050197419 11/051700 |
Document ID | / |
Family ID | 34749082 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050197419 |
Kind Code |
A1 |
Graziano, Louis Christopher ;
et al. |
September 8, 2005 |
Radiation curable aqueous binders for ink jet inks
Abstract
A polymer composition which is crosslinked and insoluble in
radiation curable monomers, prepolymers, oligomers, and mixtures
thereof, is suitable for formulation into radiation curable
compositions, for example, as binders for formulation in radiation
curable ink jet ink compositions. Such crosslinked, insoluble
polymer compositions impart improved application and curing
characteristics to ink jet ink compositions without loss of
acceptable jettability characteristics. The polymer composition may
be blended with radiation curable monomers, prepolymers, oligomers,
or mixtures thereof, to form a radiation curable binder blend for
formulation into a radiation curable ink jet ink composition. A
radiation curable ink jet ink composition including at least one
crosslinked, insoluble polymer binder composition, a liquid medium
and a colorant is also provided.
Inventors: |
Graziano, Louis Christopher;
(Doylestown, PA) ; Wu, Richard Shu-Hua; (Fort
Washington, PA) ; Lein, George Max; (Chalfont,
PA) |
Correspondence
Address: |
ROHM AND HAAS COMPANY
PATENT DEPARTMENT
100 INDEPENDENCE MALL WEST
PHILADELPHIA
PA
19106-2399
US
|
Family ID: |
34749082 |
Appl. No.: |
11/051700 |
Filed: |
February 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60549890 |
Mar 3, 2004 |
|
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Current U.S.
Class: |
522/74 |
Current CPC
Class: |
C09D 11/101
20130101 |
Class at
Publication: |
522/074 |
International
Class: |
C08K 003/00 |
Claims
What is claimed is:
1. A radiation curable polymer binder composition for formulation
into a radiation curable ink jet ink composition, wherein said
polymer composition is dispersible in an aqueous medium, is
unreactive at ambient conditions and capable of being initiated
upon exposure to actinic radiation and has a number average
molecular weight greater than 15,000 daltons.
2. The polymer composition of claim 1, wherein said polymer binder
composition has a number average molecular weight of up to
3,000,000.
3. A radiation curable binder blend comprising the radiation
curable polymer binder composition of claim 1, and a liquid medium,
wherein, when said radiation curable binder blend is formulated
into an ink jet ink composition, said ink jet ink composition is
jettable.
4. A radiation curable ink jet ink composition comprising a
colorant; a liquid medium; and an aqueous dispersion comprised of
the radiation curable polymer binder composition of claim 1.
5. The radiation curable ink jet ink composition of claim 4 wherein
said radiation curable polymer binder composition comprises 1% to
30%, by weight based on the total weight of the dry polymer
composition, of units derived from mono-ethylenically unsaturated
(meth)acrylates, multi-ethylenically unsaturated (meth)acrylates,
and mixtures thereof.
6. The radiation curable ink jet ink composition of claim 4,
wherein said liquid medium comprises at least one component
selected from the group consisting of radiation curable monomers,
radiation curable prepolymers, radiation curable oligomers, and
mixtures thereof, and wherein said liquid medium is present in an
amount of from 20 wt % to 85 wt %, based on the total weight of
said ink jet ink composition.
7. The radiation curable ink jet ink composition of claim 4,
wherein said polymer binder composition is present in an amount of
from 0.1 wt % to 25 wt %, based on the total weight of the ink jet
ink composition.
8. The radiation curable ink jet ink composition of claim 4,
wherein said colorant is present in an amount of less than 20 wt %,
based on the total weight of the ink jet ink composition.
9. A method for improving the characteristics of a radiation
curable ink jet ink composition applied to a substrate comprising
the steps of: (a) providing a radiation curable ink jet ink
composition comprising a liquid medium, a colorant and an aqueous
dispersion of at least one radiation curable polymer binder
composition which has a number average molecular weight greater
than 15,000 daltons and is dispersible in aqueous media and capable
of being initiated upon exposure to actinic radiation; (b) applying
said ink jet ink composition to a substrate; and (c) curing said
ink jet ink composition by applying actinic radiation thereby
forming an image on said substrate.
10. The method of claim 9, wherein said liquid medium comprises at
least one component selected from the group consisting of radiation
curable monomers, radiation curable prepolymers, radiation curable
oligomers, and mixtures thereof, and wherein said liquid medium is
present in an amount of from 20 wt % to 85 wt %, based on the total
weight of said ink jet ink composition.
11. The method of claim 9, wherein said at least one radiation
curable polymer binder composition is present in an amount of from
0.1 wt % to 25 wt %, based on the total weight of the ink jet ink
composition and comprises units derived from compounds selected
from the group consisting of units derived from mono-ethylenically
unsaturated (meth)acrylates, multi-ethylenically unsaturated
(meth)acrylates, and mixtures thereof
12. An image formed by the method of claim 9.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to radiation curable,
dispersible polymer binder compositions for use as components of
radiation curable ink jet ink compositions. The present invention
also relates to the radiation curable ink jet ink compositions
which comprise a liquid medium, a colorant and one or more of the
radiation curable, dispersible polymer binder composition.
BACKGROUND OF THE INVENTION
[0002] Ink jet printing is a well established technique for
applying an ink jet ink composition to a substrate, such as paper,
fabric, vinyl, leather, ceramics, polyester, or plastic, to form an
image on the substrate. Ink jet printing involves no physical
contact between the functional part of the ink jet printer from
which the ink jet ink composition is projected, or "jetted", and
the substrate onto which the ink jet ink composition is
deposited.
[0003] Generally, ink jet ink compositions are mixtures,
dispersions, solutions or suspensions, that include at least one
liquid component and at least one colorant which may be soluble
(dyes) or insoluble (pigments or dyes) in the liquid component or
components. In practice, micro-droplets of the ink jet ink
composition are projected, by well known means, through small
nozzles in the print head of the ink jet printer and onto the
substrate. After such application, the ink jet ink composition is
dried or cured, depending on the type of liquid component or
components used, to solid form on the substrate such that the
colorant, or colorants, become fixed on the substrate to form the
desired image. As discussed in further detail below, in order to
maintain the required degree of projectability, or "jettability" as
it is referred to in the art, of the ink jet ink composition, they
have heretofore been formulated to have relatively low viscosities
and include substances having relatively small particle sizes.
[0004] Ink jet ink compositions may be water-based (i.e., aqueous),
solvent-based, oil-based, or 100% solids. This nomenclature
differentiates the ink jet ink compositions in terms of how much of
the ink jet ink composition is left behind on the substrate after
drying or curing. Water-based, solvent-based, and oil-based ink jet
ink compositions will lose at least a portion of the liquid
component to evaporation during the post-application drying or
curing step, such that only a portion of the mass of the ink jet
ink composition remains on the substrate to form the desired image.
On the other hand, the drying or curing step will convert
substantially all of the liquid component or components of 100%
solids ink jet ink compositions to solid form such that
substantially all of the mass of a 100% solids ink jet ink
composition remains on the substrate to form the desired image.
[0005] Any of the foregoing four types of ink jet ink compositions
(i.e., aqueous, solvent-based, oil-based and 100% solids) may be
radiation curable, which means that they can be cured by exposure
to actinic radiation. Typically, radiation curable ink jet ink
compositions require the inclusion of mixtures of radiation curable
monomers, or such monomers mixed with low molecular weight
radiation curable oligomers. Such monomers and oligomers are
typically in liquid form and are unreactive at ambient conditions,
but are capable of being initiated to react and crosslink with
themselves and/or each other by exposure to actinic radiation, such
as ultraviolet (UV) radiation or electronic beam (E-beam)
radiation. It is known that where UV radiation is to be used to
initiate such monomers and/or oligomers, it is often necessary to
also include photoinitiators in the mixture of radiation curable
monomers and/or oligomers. The reacting and crosslinking of the
radiation curable monomers and/or oligomers converts them to solid
form and binds the colorant or colorants of the ink jet ink
composition onto the substrate.
[0006] Radiation curable monomers and/or oligomers, as well as
certain polymer compositions, may act as "binders" when included in
ink jet ink compositions. The use of such polymer binders is known
to improve various properties of the ink compositions, as well as
the images created therefrom. Such improved properties include, but
are not limited to, abrasion resistance, wash resistance, smear
resistance, permanence, gloss, adhesion and optical properties. It
is also known that as the molecular weight of the polymer binder
constituents increases, the aforesaid properties of the ink
compositions and images formed therefrom can be further
improved.
[0007] Thus, on the one hand, it would be advantageous to use
polymer binders having relatively high molecular weights in ink jet
ink compositions. However, it is also known that, as mentioned in
U.S. Pat. No. 6,294,592, it is important to control the viscosity
of ink jet ink compositions, in part, to maintain the desired
jettability of the ink compositions (i.e., to ensure that the ink
jet ink compositions can be effectively projected from the small
nozzles of the ink jet printer). In practice this means that it is
often important to keep the viscosities of ink jet ink compositions
relatively low.
[0008] Unfortunately, as the molecular weight of the polymer binder
compositions used in radiation curable ink jet ink compositions
increases, the viscosity of the ink jet ink compositions also
typically increases, sometimes to the point of interfering with
jettability of the ink composition. In addition, high molecular
weight binders may dry or coagulate at the nozzle surface resulting
in poor jettability of the ink. Thus, to ensure jettability of
radiation curable ink jet ink compositions, the molecular weight of
the polymer binders must also be low enough to form an ink
composition having sufficiently low viscosity and demonstrating the
ability to be ejected from the printhead for extended periods of
time without clogging or misdirecting. As a result, the use of
polymer binders for radiation curable ink jet ink compositions is
often limited to the inclusion of monomeric, macromonomeric and
oligomeric binder constituents having a number average molecular
weight, M.sub.n, of not more than about 15,000 in order to
effectively jet the ink from the nozzles of the printhead.
[0009] For example, U.S. Pat. No. 6,294,592 discloses the use of
radiation curable binder compositions, including acrylate,
polyurethane, vinyl and/or epoxy monomers, prepolymers and
polymers, and mixtures thereof, in aqueous emulsion form, as
binders for curable aqueous ink jet ink compositions. However, the
constituents of the binder compositions of U.S. Pat. No. 6,294,592
are limited to having number average molecular weight (M.sub.n) of
about 15,000 or less. In addition, the use of isocyanate
functionality is required, which can give rise to toxicity concerns
as well as stability issues with regard to high reactivity of
isocyanate and water.
[0010] WO 02/064689 discloses aqueous ink jet ink compositions that
include UV curable binder compositions comprising oligomers or
prepolymers, which are dilutable in the aqueous medium of the ink
composition. The oligomers and prepolymers have a molecular weight
of from about 2,000 to about 10,000 and may include unsaturated
urethane, acrylic, polyester and epoxy resins, and mixtures
thereof. Furthermore, the oligomers and prepolymers have a mean
particle size of about 30 nanometers to about 80 nanometers.
[0011] Ink jet ink compositions containing soluble, low molecular
weight (M.sub.n) radiation curable polymers, such as those
described in the above references, are typically limited in the
amount of the polymer binder that can be included in ink jet ink
compositions due to the viscosity contributions of the polymer.
[0012] There is a need for polymer binder compositions having a
high molecular weight which can be used in radiation curable ink
jet ink compositions and which would achieve further improvements
to the properties of the ink jet ink compositions and the images
formed therefrom. Such ink jet ink compositions can exhibit
improved durability, such as wash-fastness or smear resistance,
due, it is believed, to increased adhesion and flexibility that can
be imparted to the ink jet ink composition by the high molecular
weight polymer binder, when the ink composition is applied to a
substrate and cured to form an image thereon.
[0013] In addition, there is a need to minimize the increase in
viscosity of a curable ink composition that includes such higher
molecular weight polymer binders when reactive monomers,
prepolymers, and/or oligomers are added, so that the ink jet ink
compositions can be formulated with a higher resin content. The
ability to formulate ink jet ink compositions with high resin
content can result in improved application properties of the ink
compositions, such as improved early set resulting in better image
quality, as compared to traditional radiation cured inks, and
improved holdout on porous media such as paper and textiles.
Benefits in flexibility of such ink compositions can also be
realized due to the ability to design resin softness into such ink
compositions.
[0014] The problem addressed by the present invention is to provide
radiation curable, dispersible polymer binder compositions for use
in ink jet ink compositions and which are capable of imparting
improvements to the aforementioned characteristics of the ink
composition into which they are formulated, while avoiding
unacceptable increases in viscosity of the ink composition which
otherwise can result in poor jettability, or even total failure to
jet, of the ink composition.
SUMMARY OF THE INVENTION
[0015] A radiation curable polymer binder composition is provided
for formulation into a radiation curable ink jet ink composition.
The radiation curable polymer binder composition is dispersible in
an aqueous medium, is unreactive at ambient conditions and capable
of being initiated upon exposure to actinic radiation and has a
number average molecular weight greater than 15,000 daltons. The
polymer composition may have a number average molecular weight of
up to 3,000,000.
[0016] A radiation curable binder blend is also provided which
comprises the aforesaid radiation curable polymer binder
composition and a liquid medium, and when the radiation curable
binder blend is formulated into an ink jet ink composition, the ink
jet ink composition is jettable.
[0017] The present invention further provides a radiation curable
ink jet ink composition which comprises: a colorant; a liquid
medium; and an aqueous dispersion comprised of the aforesaid
radiation curable polymer binder composition. In the radiation
curable ink jet ink composition, the said radiation curable polymer
binder composition comprises 1% to 30%, by weight based on the
total weight of the dry polymer composition, of units derived from
mono-ethylenically unsaturated (meth)acrylates, multi-ethylenically
unsaturated (meth)acrylates, and mixtures thereof. The liquid
medium of the radiation curable ink jet ink composition comprises
at least one component selected from the group consisting of
radiation curable monomers, radiation curable prepolymers,
radiation curable oligomers, and mixtures thereof, and is present
in an amount of from 20 wt % to 85 wt %, based on the total weight
of said ink jet ink composition.
[0018] The present invention also provides a method for improving
the characteristics of a radiation curable ink jet ink composition
applied to a substrate comprising the steps of (a) providing a
radiation curable ink jet ink composition comprising a liquid
medium, a colorant and an aqueous dispersion of at least one
radiation curable polymer binder composition which has a number
average molecular weight greater than 15,000 daltons and is
dispersible in aqueous media and capable of being initiated upon
exposure to actinic radiation; (b) applying said ink jet ink
composition to a substrate; and (c) curing said ink jet ink
composition by applying actinic radiation thereby forming an image
on the substrate. The image thus formed is also within the scope of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention relates to polymer compositions which
are radiation curable and dispersible in aqueous media and suitable
for use in radiation curable compositions. Such radiation curable
compositions find application in various fields, including, but not
limited to, coatings such as paints and inks, especially aqueous
ink jet ink compositions, and adhesives. For example, radiation
curable ink jet ink compositions that are formulated with the
radiation curable, dispersible polymer binder compositions of the
present invention typically comprise a liquid medium, a colorant
and at least one radiation curable, dispersible polymer binder
composition.
[0020] Definitions and conventions relating to certain terminology
and measurements that are used throughout the following discussion
are as follows.
[0021] The term "aqueous" medium, as used herein, means a medium
that is from 40% to 100% water, by weight, based on the total
weight of the aqueous medium, with the remainder of the aqueous
medium being, optionally, comprised of suitable solvents,
dispersants, emulsifiers, etc.
[0022] As used herein, the term "dispersion" refers to a physical
state of matter that includes at least two distinct phases wherein
a first phase is distributed in a second phase, the second phase
being a continuous medium.
[0023] As used herein, the term "molecular weight" refers to the
number average molecular weight of polymer molecules as determined
by gel permeation chromatography using polystyrene as a standard
and tetrahydrofuran as the mobile phase.
[0024] The term "units derived from" used herein refers to polymer
molecules that are synthesized according to known polymerization
techniques wherein a polymer contains "units derived from" its
constituent monomers, prepolymers and/or oligomers.
[0025] The term "dispersible" is used herein to describe polymer
materials which, when mixed, blended, or otherwise combined, with a
liquid medium, the polymer material maintains its identity as
particles. Moreover, when "dispersible" polymer materials are
formulated into an ink jet ink composition, the viscosity of the
ink jet ink composition does not appreciably increase, but rather
the viscosity remains no greater than about 0.15 Pa.multidot.s, as
measured using a Brookfield Viscometer Model DV-II with a
Brookfield UL Adapter and recorded at a spindle speed of 20
rpm.
[0026] As is well known in the art, the glass transition
temperature, Tg, of a polymer can be estimated using the Fox
equation (Bulletin of the American Physical Society 1, 3, page 123
(1956)), which is as follows: 1 1 T g = w 1 T g ( 1 ) + w 2 T g ( 2
)
[0027] For a copolymer including monomers M.sub.1 and M.sub.2,
w.sub.1 and w.sub.2 refer to the weight fraction of the two
monomers, respectively, and T.sub.g(1) and T.sub.g(2) refer to the
glass transition temperatures, in degrees Kelvin, of the two
corresponding homopolymers derived from monomers M.sub.1 and
M.sub.2. The glass transition temperatures of various homopolymers
can be found, for example, in "Polymer Handbook", edited by J.
Brandrup and E. H. Immergut, Interscience Publishers. For polymers
containing three or more monomers, additional terms are added
(i.e., 1/T.sub.g=.SIGMA.(w.sub.n/T.sub.g(n)). Although the T.sub.g
of a polymer can also be measured by various other techniques, the
particular values of T.sub.g reported hereinafter are calculated
based on the Fox equation provided above.
[0028] As used herein, the term "(meth)acrylates" is intended to
include both acrylate and methacrylate types of monomers.
[0029] As used herein, the term "radiation curable" means that the
particular compositions being discussed are unreactive at ambient
conditions, but capable of being initiated to react and crosslink
with themselves and/or other radiation curable compounds (i.e.,
"cured"), by exposure to actinic radiation, such as ultraviolet
(UV) radiation or electronic beam (E-beam) radiation.
[0030] The term "ambient conditions" as used herein in connection
with radiation curable compounds refers to ambient temperatures of
from about 15.degree. C. to 40.degree. C. and ambient pressure of
about 1 atmosphere.
[0031] All percentages used herein to describe the compositional
constituents of the various embodiments of the present invention,
unless otherwise specified, are weight percents based upon the
total weight of the particular composition, latex, mixture, etc.
being discussed.
[0032] All ranges defined herein are inclusive and combinable.
[0033] Although the radiation curable, dispersible polymer binder
composition of the present invention may be useful in other types
of radiation curable compositions, including various types of
coatings or adhesives, as would be understood by persons of
ordinary skill in the relevant art, the discussion and description
which follow focus on application of the polymer compositions of
the present invention as binders for formulation into radiation
curable ink jet ink compositions. Furthermore, while the radiation
curable, dispersible polymer binder compositions of the present
invention will be described hereinafter in particular in connection
with aqueous (also known as latex) radiation curable ink jet ink
compositions, it is understood that they may also be useful for
other types of ink jet ink compositions.
[0034] A first embodiment of the present invention comprises
polymer binder compositions which are radiation curable,
dispersible in aqueous media, and suitable for formulating into
radiation curable aqueous ink jet ink compositions. Without
intending to be limited by theory, it is believed that the
dispersibility of the polymer composition reduces viscosity
increases such that, when the polymer binder compositions are
formulated into a radiation curable ink jet ink composition, the
ink jet ink composition remains jettable through conventional ink
jet ink printing apparatus. The radiation curable, dispersible
polymer binder compositions comprise, as polymerized units, at
least one unreacted radiation curable functionality which is
unreactive at ambient conditions and capable of reacting upon
exposure to actinic radiation.
[0035] In addition, the radiation curable, dispersible polymer
binder compositions have a number average molecular weight
(M.sub.n) of from greater than about 15,000 to about 3,000,000.
[0036] The inclusion of such radiation curable, dispersible polymer
binder compositions in radiation curable aqueous ink jet ink
compositions may result in improvements to one or more of the
following characteristics of the ink compositions: jettability,
substrate holdout, adhesion, abrasion resistance, wash resistance,
smear resistance, flexibility or optical properties.
[0037] More particularly, the radiation curable, dispersible
polymer binder compositions of the present invention comprise, as
polymerized units, from 1 wt % to 30 wt %, based on the total
weight of the dry radiation curable, dispersible polymer binder
composition, of one or more curable compositions which are
unreactive at ambient conditions and are capable of being initiated
via actinic radiation. The aforesaid one or more curable
compositions comprise, without limitation, for example,
multi-ethylenically-unsaturated monomers as described in
EP1245644A2 and include, but are not limited to di-, tri-, tetra-,
or higher multi-functional ethylenically unsaturated monomers. Such
multi-functional ethylenically unsaturated monomers include, for
exmaple, without limitation, one or more types of
(meth)acrylates.
[0038] The remainder of the radiation curable, dispersible polymer
binder compositions may comprise, as polymerized units, from 99 wt
% to 70 wt %, based on the total weight of the dry radiation
curable, dispersible polymer binder composition, one or more
monomers including, but not limited to, those described in
EP1245644A2, such as, (meth)acrylate monomers, (meth)acrylic acid,
C.sub.1-C.sub.12 (meth)acrylates, (meth)acrylamides,
methylolacrylamides, C.sub.8-C.sub.22 alkenyl (meth)acrylates,
aromatic (meth)acrylates, phosphorus-containing compounds such as
phosphoethyl (meth)acrylate, amine functional (meth)acrylates, and
hydroxy alkyl (meth)acrylates.
[0039] The radiation curable, dispersible polymer binder
compositions of the present invention typically have number average
molecular weight (M.sub.n) in the range of from greater than about
15,000 to about 3,000,000, including from 15,000 to 2,000,000 and
even from 25,000 to 1,500,000.
[0040] The glass transition temperature ("Tg") of the radiation
curable, dispersible polymer binder compositions is typically from
-50.degree. C. to 150.degree. C., for example from -25.degree. C.
to 120.degree. C., and even from -10.degree. C. to 100.degree. C.,
the exact preferred Tg depending on the application for which the
ink is being used. The monomers and amounts of the monomers used to
prepare the radiation curable, dispersible polymer binder
compositions are selected, as is well-known to persons of ordinary
skill in the art, to achieve the desired polymer Tg range.
[0041] In addition, the radiation curable, dispersible polymer
binder compositions have an average particle diameter of from about
1 to 1000 nanometers ("nm"), such as from about 20 to 500 nm, or
from about 50-300 nm, as determined using a Brookhaven Model BI-90
particle sizer manufactured by Brookhaven Instruments Corporation,
Holtsville N.Y., reported as "effective diameter". It is also
contemplated that the radiation curable, dispersible polymer binder
compositions of the present invention may include multimodal
particle size emulsion polymers, wherein two or more distinct
particle sizes, or very broad distributions, are provided, as is
taught in U.S. Pat. Nos. 5,340,858; 5,350,787; 5,352,720;
4,539,361; and 4,456,726, each of which are hereby incorporated
herein in their entireties.
[0042] The radiation curable, dispersible polymer binder
compositions of the present invention are typically prepared using
emulsion addition polymerization, but can also be prepared using
other polymerization methods such as dispersion, solution,
suspension or condensation polymerization. For example, a radiation
curable, dispersible polymer binder composition prepared using a
condensation polymerization method may, for example, be comprised
of from 1 to 30 wt % hydroxy functional (meth)acrylate monomer,
such as hydroxy ethyl (meth)acrylate, and multi-functional hydroxy
functional compounds, and mono- and multi-functional isocyanate
compounds. Examples of such multi-functional hydroxy compounds
include but are not limited to trimethylolpropane, hexanediol, and
polymers or oligomers derived from hydroxy functional monomers such
as for example phenoxy ethyl (meth)acrylate,
cyclictrimethylolpropane formal mono(meth)acrylate, 1,6-hexanediol
diacrylate, alkoxylated pentaerythritol tetraacrylate,
polycaprolactone polyol, and polypropylene glycol. Examples of such
multifunctional isocyanate compounds include but are not limited to
toluene diisocyanate, methylenedisocyanate, isophorone disocyanate,
trimethylhexamethylene diisocyanate, and xylylene diisocyanate.
[0043] Furthermore, the radiation curable, dispersible polymer
binder compositions of the present invention can be combined with
other reactive or non-reactive binders which have a
M.sub.n<25,000 and which may be soluble or dispersible in a
liquid medium containing the radiation curable binder
composition.
[0044] Furthermore, where it is desirable to provide additional
radiation curable functionalities to the radiation curable,
dispersible polymer binder compositions, one or more of them may
also contain the following compounds, either alternatively or in
combination, as polymerized units:
[0045] a. at least one multiethylenically unsaturated monomer,
and
[0046] b. at least one monoethylenically unsaturated monomer which
has a reactable functionality that can be reacted with a modifying
compound which, in turn, contains a complementary reactable group,
reactable by either ionic or covalent bonding, as well as a
radiation curable functional group that can be reacted through
exposure to actinic radiation. Whether the reaction between the
reactable functionality and the complemetary functional group (the
complementary bonding pair) is ionic or covalent, the first or
second member of each complementary bonding pair may be present
either in the polymer binder composition or, alternatively, in the
modifying compound.
[0047] Inclusion of multiethylenically unsaturated monomers, as
polymerized units, in the radiation curable, dispersible polymer
binder compositions provides radiation curable functionality to the
polymer binder compositions. More particularly, suitable
multiethylenically unsaturated monomers useful in the present
invention include di-, tri-, tetra-, or higher multifunctional
ethylenically unsaturated monomers, such as, for example,
trivinylbenzene, divinyltoluene, divinylpyridine,
divinylnaphthalene and divinylxylene; and such as ethyleneglycol
diacrylate, trimethylolpropane triacrylate, diethyleneglycol
divinyl ether, trivinylcyclohexane, allyl methacrylate ("ALMA"),
ethyleneglycol dimethacrylate ("EGDMA"), diethyleneglycol
dimethacrylate ("DEGDMA"), propyleneglycol dimethacrylate,
propyleneglycol diacrylate, trimethylolpropane trimethacrylate
("TMPTMA"), divinyl benzene ("DVB"),
2,2-dimethylpropane-1,3-diacrylate, 1,3-butylene glycol diacrylate,
1,3-butylene glycol dimethacrylate, 1,4-butanediol diacrylate,
diethylene glycol diacrylate, diethylene glycol dimethacrylate,
1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate,
tripropylene glycol diacrylate, triethylene glycol dimethacrylate,
tetraethylene glycol diacrylate, polyethylene glycol 200
diacrylate, tetraethylene glycol dimethacrylate, polyethylene
glycol dimethacrylate, ethoxylated bisphenol A diacrylate,
ethoxylated bisphenol A dimethacrylate, polyethylene glycol 600
dimethacrylate, poly(butanediol) diacrylate, pentaerythritol
triacrylate, trimethylolpropane triethoxy triacrylate, glyceryl
propoxy triacrylate, pentaerythritol tetraacrylate, pentaerythritol
tetramethacrylate, dipentaerythritol monohydroxypentaacrylate,
divinyl silane, trivinyl silane, dimethyl divinyl silane, divinyl
methyl silane, methyl trivinyl silane, diphenyl divinyl silane,
divinyl phenyl silane, trivinyl phenyl silane, divinyl methyl
phenyl silane, tetravinyl silane, dimethyl vinyl disiloxane,
poly(methyl vinyl siloxane), poly(vinyl hydro siloxane), poly
(phenyl vinyl siloxane), and mixtures thereof.
[0048] With reference to the above-described monoethylenically
unsaturated monomers, it is noted that their inclusion, as
polymerized units, in one or more of the radiation curable,
dispersible polymer binder compositions, would not itself provide
the polymer binder compositions with radiation curable
functionalities. However, when the monoethylenically unsaturated
monomers contain secondary reactable functionality, the resultant
polymer composition can be reacted with the complementary reactable
group of a suitable modifying compound which also contains a
radiation curable functional group. This results in the
incorporation of a radiation curable functionality in the radiation
curable, dispersible polymer binder composition.
[0049] In practice, after initial formation of the dispersible
polymer binder compositions by any of the conventional known
polymerization techniques mentioned above, but prior to formulation
of the polymer binder composition into a radiation curable ink
composition, suitable modifying compounds are blended and reacted
with the dispersible polymer binder compositions such that the
modifying compounds would be chemically combined with the
dispersible polymer binder compositions and their radiation curable
functionalities would still be available for reaction by exposure
to actinic radiation. In the foregoing manner, radiation curable
functional groups are incorporated into the radiation curable,
dispersible polymer binder compositions.
[0050] Where the reactable functionality of the radiation curable,
dispersible polymer binder compositions and the complementary
reactable group of the modifying compound are ionic complementary
bonding pairs, their bonding may involve acid-base interaction
and/or ion pair bonding of negatively and positively charged atoms.
Where ionic complementary bonding pairs are to be used, suitable
modifying compounds include, but are not limited to, (meth)acrylic
acid, crotonic acid, dicarboxylic acid monomers such as itaconic
acid, maleic acid, and fumaric acid, 2-acrylamido-2-methyl propane
sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid; and
phosphorous acid monomers such as 2-phosphoethyle (meth)acrylate,
vinyl phosphoric acid, vinyl phosphinic acid, N,N-dimethyl
aminoethyl(meth)acrylate, and N-ethyldimethylallyl amine.
[0051] Covalent bonding, may be achieved with complementary
reaction groups such as, for example: (a) acetoacetate-aldehyde;
(b) acetoacetate-amine; c) amine-aldehyde; (d) hydroxyl-anhydride;
(e) amine-isocyanate; (f) amine-epoxy; (g) aldehyde-hydrazide; (i)
acid-epoxy; (j) acid-carbodiimide; (k) acid-chloro methyl ester;
(j) acid-chloro methyl amine; (m) acid-anhydride; (n)
acid-aziridine; (o) epoxy-mercaptan; (p) alcohol-epoxy; and (q)
isocyanate-alcohol. Where complementary bonding pairs are to be
used, either reacting functionality can reside in the dispersible
polymer binder, or in the modifying compound. Where covalent
complementary bonding pairs are to be used, suitable modifying
compounds include, but are not limited to, unsaturated monoepoxides
including glycidyl (meth)acrylate, allyl glycidyl ether, glycidyl
cinnamates, glycidyl crotonares, glycidyl itaconates, glycidyl
norbornenyl ester, glycidyl norbornenyl ether, N-t-butylaminoethyl
(meth)acrylate, (meth)acrylic acid, dimethyl aminoethyl
methacrylate, and the like.
[0052] The radiation curable, dispersible polymer binder
compositions of the present invention may or may not be homogeneous
in their compositional distribution. For example, in a particular
embodiment of the present invention, one or more of the radiation
curable, dispersible polymer binder compositions may be multistage
core/shell polymers, whereby the the first stage contains units
derived from monomers that give a soft, elastomeric composition,
and later stages contain units derived from monomers that give a
polymeric composition that is harder than the first stage.
[0053] In a second embodiment of the present invention, an aqueous,
or "latex", binder dispersion is provided which comprises an
aqueous dispersion of at least one (i.e., one or more) of the
radiation curable, dispersible polymer binder compositions
described hereinabove in connection with the first embodiment of
the present invention in an aqueous medium. The aforementioned
polymerization techniques which may be used to prepare the
radiation curable, dispersible polymer binder compositions of the
present invention may, with minimal processing after
polymerization, result in the formation of this aqueous, or
"latex", binder dispersion.
[0054] In a third embodiment of the present invention, a radiation
curable latex binder blend is provided for formulation into a
radiation curable aqueous ink jet ink composition. The curable
latex binder blend is an aqueous dispersion comprising at least one
radiation curable, dispersible polymer binder composition of the
type described hereinabove and a liquid medium. The liquid medium
of the aqueous dispersion of the radiation curable latex binder
blend is an additional aqueous medium, which may be the same as, or
different from, or in addition to, the aqueous medium which is
formed by the polymerization technique used to prepare the
radiation curable, dispersible polymer binder compositions. The
radiation curable, dispersible polymer binder compositions are
dispersed in the aqueous medium to form the curable latex binder
blend in accordance with the present invention. The curable latex
binder blend of the present invention is capable of being
formulated into a curable latex ink composition, along with
suitable colorants, such that the ink composition remains capable
of being jetted through an ink jet printhead.
[0055] The curable latex binder blend may further include typical
radiation curable monomers, typical curable oligomers, or mixtures
thereof, to further enhance the performance properties of the
curable latex ink composition which is formulated therewith, as
long as the viscosity of the resulting ink composition is not
increased to the point where the ink composition is no longer
jettable from the ink jet print head. The radiation curable
monomers and oligomers are unreactive at ambient conditions and
capable of being initiated when exposed to actinic radiation such
that they react with each other and also with the curable high
molecular weight crosslinked polymer binder (or binders).
[0056] Suitable radiation curable monomers for use in the curable
latex binder blend include, without limitation, hexanediol
diacrylate, trimethylolpropane triacrylate, pentaerythritol
triacrylate, 10 polyethyleneglycol diacrylate, for example,
tetraethyleneglycol diacrylate, dipropyleneglycol diacrylate,
tri(propylene glycol) triacrylate, neopentylglycol diacrylate,
bis(pentaerythritol) hexa-acrylate, and the acrylate esters of
ethoxylated or propoxylated glycols and polyols, for example,
propoxylated neopentyl glycol diacrylate, isodecyl (meth) acrylate,
ethoxylated trimethylolpropane triacrylate, triethylene glycol
divinyl ether, diethylene glycol divinyl ether,
1,4-cyclohexanedimethanol divinyl ether and ethylene glycol
monovinyl ether, as well as ethyl-1 propenyl ether,
triethyleneglycol methyl propenyl ether, triethyleneglycol methyl
vinyl ether and 2-cyclopenten-1-yl ether, and mixtures thereof.
[0057] Suitable radiation curable oligomers for use in the curable
latex binder blend of the present invention include, without
limitation, CN985, CN975, CN301 and CN501 available from Sartomer
Company, Exton, Pa., USA.
[0058] A fourth embodiment of the present invention provides a
radiation curable aqueous ink jet ink composition which comprises a
liquid medium, a colorant and the latex binder blend described
hereinabove. The liquid medium is typically predominantly water,
preferably deionized water. The curable aqueous ink composition of
the present invention may include the radiation curable latex
binder blend in an amount of from 0.1% to 25 %, such as from 1% to
20%, by weight based on the total weight of the curable aqueous ink
composition.
[0059] Suitable colorants for use in the aqueous ink jet ink
composition may be pigments, dyes or mixtures thereof. Moreover,
the pigment may be an organic pigment or an inorganic pigment.
Suitable organic pigments that can be used in the formulated ink
include, for example, surface modified and unmodified,
anthroquinones, phthalocyanine blues, phthalocyanine greens,
diazos, monoazos, heterocyclic yellows, pyranthrones, quinacridone
pigments, dioxazine pigments, indigo, thioindigo pigments, perynone
pigments, perylene pigments, isoindolene, polymer particles having
at least one void, and the like. Carbon black is the generic name
for small particle size carbon particles formed in the gas phase by
the thermal decomposition of hydrocarbons and includes, for
example, materials known in the art as furnace black, lampblack,
channel black, acetylene black. Carbon black additionally
encompasses treated, modified, and oxidized cabon black. Suitable
inorganic pigments include titanium dioxide, iron oxide, and other
metal powders. Generally, the amount of pigment(s) used is less
than 20%, preferably 3-8%, more preferably 2-6% by weight based on
the total weight of the latex ink composition. Polymer dispersed
pigments used in this invention may be stabilized using random or
block copolymer dispersants, or mixtures thereof. Dyes suitable as
colorants for use in this invention include water soluble dyes,
dispersed dyes and polymer dispersed dyes, such as for example
those described in WO0250197A1 and U.S. Pat. No. 6,455,611B1, or
mixtures thereof.
[0060] In the case where ultraviolet radiation is used to initiate
the reaction, the aqueous ink jet ink composition includes a
photoinitiator, or combination of photoinitiators that can react
with the radiation curable functionalities of the radiation
curable, dispersible polymer binder composition to start a
crosslinking reaction. Any photoinitiator known in the art can be
used to initiate the reaction. It is preferred that the
photoiniator(s) is dispersable or soluble in water. The
photoinitiator(s) should be chosen such that the absorption of the
photoinitiator is optimized for particular colorants being used in
the ink, and for the lamp source being used, which would be within
the ability of persons having ordinary skill in the art. If
desired, a photoinitiator synergist may be used to enhance cure and
reduce oxygen inhibition.
[0061] The radiation curable aqueous ink composition may also
include water miscible or soluble materials such as polymers other
than the curable dispersible binder polymers of this invention,
humectants, dispersants, penetrants, chelating agents, co-solvents,
defoamers, buffers, biocides, fungicides, viscosity modifiers,
bactericides, surfactants, anti-curling agents, anti-bleed agents
and surface tension modifiers, all as are well known to persons of
ordinary skill in the art.
[0062] For example, suitable humectants include, without
limitation, ethylene glycol, 1,3-propanediol, 1,4-butanediol,
1,4-cyclohexanedimethan- ol, 1,5-pentanediol, 1,6-hexanediol,
1,8-octanediol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol,
2,3-butanediol, diethylene glycol, triethylene glycol,
tetraethylene glycol, polyethylene glycol with average molecular
weight of 200, 300, 400, 600, 900, 1000, 1500 and 2000, dipropylene
glycol, polyproylene glycol with average molecular weight of 425,
725, 1000, and 2000, 2-pyrrolidone, 1-methyl-2-pyrrolidone,
1-methyl-2-piperidone, N-ethylacetamide, N-methlpropionamide,
N-acetyl ethanolamine, N-methylacetamide, formamide,
3-amino-1,2-propanediol, 2,2-thiodiethanol, 3,3-thiodipropanol,
tetramethylene sulfone, butadiene sulfone, ethylene carbonate,
butyrolacetone, tetrahydrofurfuryl alcohol, glycerol,
1,2,4-butenetriol, trimethylpropane, pantothenol, Liponic EG-1.
Preferred humectants are polyethylene glycol with average molecular
weight of 400 to 1000, 2-pyrrolidone 2,2-thiodiethanol, and
1,5-pentanediol. The amount of humectant used is determined by the
properties of the ink and may range from 1-30%, preferably 5-15%,
by weight, based on the total weight of the ink.
[0063] Preferred penetrants include n-propanol, isopropyl alcohol,
1,3-propanediol, 1,2-hexanediol, and hexyl carbitol. The use of
suitable penetrants will depend on the specific application of the
ink. Useful examples include, but are not limited to, pyrrolidone,
and N-methyl-2-pyrrolidone.
[0064] Examples of suitable chelating agents include, but are not
limited to: EDTA and salts thereof, organo-phosphonic acids and
salts thereof. When chelating agents are included in the curable
aqueous ink formulation they are typically added at concentrations
of from 0.05% to 20% by weight based on the total weight of the
curable aqueous ink formulation.
[0065] Defoaming agents useful in forming aqueous dispersions of
pigments are well known in the art and commercially available
examples include Surfynol 104H and Surfynol DF-37 (Air Products,
Allentown, Pa.). The amount of defoaming agent in the curable
aqueous ink composition will typically range from 0% to 0.5% by
weight, based on the total weight of the curable aqueous ink
composition.
[0066] The radiation curable aqueous ink composition of the present
invention may be prepared by any method known in the art for making
such compositions, for example, by mixing, stirring or agitating
the ingredients together using any art recognized technique to form
an aqueous ink. The procedure for preparation of the ink
composition of the present invention is not critical except to the
extent that the ink composition is homogenous.
[0067] A fourth embodiment of the present invention provides a
method for improving the durability of a radiation curable ink jet
ink composition applied to a substrate comprising: (a) forming a
aqueous ink jet ink composition comprising a liquid medium, a
colorant, a radiation curable, dispersible polymer binder
composition which is unreactive at ambient conditions and are
capable of being intiated via actinic radiation; (b) applying the
ink jet ink composition onto a substrate; and (c) curing the ink
jet ink composition by applying ultraviolet or electronic beam
radiation to the ink composition.
[0068] As used herein, the term "durability" is intended to
include, but not necessarily be limited to, ink composition
properties such as substrate holdout, adhesion, abrasion
resistance, wash resistance, smear resistance and flexibility.
[0069] The aqueous ink jet ink compositions of the present
invention are suitable for application by one of the ink jet
techniques known in the art using, for example, thermal or bubble
jet printers, piezoelectric printers, continuous flow printers, air
brush or valve jet printers, to a substrate. Preferred substrates
are fabrics, either woven or nonwoven, which may be formed from
suitable fibers such as, for example, cotton, polyester, aramid,
silk, acrylic, wool, rayon, nylon, polyamide, and glass. Any
suitable substrate may be utilized, including paper, vinyl, leather
and polyester. After application to a suitable substrate, the ink
composition is then cured, preferrably through exposure to actinic
radiation such as ultraviolet (UV) or electron-beam (E-beam)
radiation. As will be understood by persons of ordinary skill in
the art, curing conditions used for the ink compositions of the
present invention will vary depending on ink film thickness,
colorant, and substrate. Generally, a cure dose of about 300 mJ/cm2
to 700 mJ/cm2 is sufficient to enact curing. A UV lamp source with
a broad range of wavelength, such as that achievable with a iron
doped or gallium doped UV lamp, is preferred when curing ink films
greater than 6 microns in thickness, or when curing ink
compositions containing colorants that absorb radiation in the
wavelength region characteristic of a typical H bulb.
EXAMPLES
[0070] The abbreviations listed below are used throughout the
following examples:
[0071] ALMA=allyl methacrylate
[0072] AMPS=2-acrylamido-2-methylpropane sulfonic acid
[0073] BA=butyl acrylate
[0074] DVB=divinylbenzene
[0075] EA=ethyl acrylate
[0076] FMA=furfuryl methacrylate
[0077] GMA=glycidyl methacrylate
[0078] IBOA=isobornyl acrylate
[0079] MAA=methacrylic acid
[0080] MMA=methyl methacrylate
[0081] TBAEMA=N-t-butylaminoethyl (meth)acrylate
[0082] TMPTA=trimethylol propane triacrylate
Example 1
Radiation Curable Latex Binder for Radiation Curable Aqueous Ink
Jet Ink Composition
[0083] Latex A is a radiation-curable latex dispersion formed by
making a single stage emulsion polymer of composition 60 wt % EA/22
wt % Styrene/3 wt % MAA/10 wt % DVB/5 wt % ALMA. Thus, a monomer
emulsion is made by mixing 60 grams ("g") of EA, 22 g of styrene, 3
g of MAA10 g of DVB and 5 g of ALMA and 1.5 g of sodium laurel
sulfate in 28% aqueous solution (hereinafter "SLS (28%)") and 100 g
of water. Into the reactor is charged 82 g of water and 4.5 g of
SLS (28%). This is then heated to 50.degree. C. At 50.degree. C., a
solution consisting of 0.003 g ferrous sulfate heptahydrate, 0.056
g of sodium salt of ethylene diamine tetraacetic acid and 3 g
de-ionized (hereinafter "DI") water is added to the kettle. After 1
minute, 20 g of the monomer emulsion above is charged into the
reactor. An initial catalyst solution consisting of 0.054 g
ammonium persulfate, 0.04 g 70% t-butyl hydroperoxide, and 5 g DI
water is added, followed by the addition of an initial activator
solution consisting of 0.05 g sodium bisulfite and 0.02 g sodium
hydrosulfate dissolved in 5 g DI water. After waiting 10 minutes, a
cofeed solution consisting of 0.143 g 70% t-butyl hydroperoxide in
9 g DI water along with a separate cofeed solution of 0.125 g
sodium bisulfite in 9 g DI water is initiated. Simultaneously, a
gradual addition of the remaining monomer emulsion is initiated.
The total feed time for the monomer emulsion and initiator feeds is
90 minutes. When all feeds are complete, the reactor is held at
55.degree. C. for an additional 20 minutes. Aqueous solutions of
t-butyl hydroperoxide (70%) and sodium formaldehyde sulfoxylate are
added sequentially with 20-minute hold periods at 55.degree. C.
[0084] Latex A produced by the foregoing procedure will be a
radiation curable latex binder blend, in accordance with the
present invention, that is suitable for formulating into a
radiation curable aqueous ink jet ink composition. Latex A should
have approximately 15 wt % solids content, based on the total
weight of Latex A. In the event that the solids content of Latex A
is greater than the desired 15 wt %, water or another suitable
aqueous medium is added and mixed therewith to attain the desired
15 wt %. More particularly, the solids component of Latex A
includes a radiation curable, dispersible polymer binder
composition that contains functionalities in the form of covalently
bound unreacted double bonds which are available for initiation
upon exposure to UV radiation. The radiation curable, dispersible
polymer binder composition is expected to have a molecular weight
of from about 500,000 to about 2,500,000.
Example 2
Radiation Curable Latex Binder Blend for Radiation Curable Aqueous
Ink Jet Ink Composition
[0085] Latex B is a radiation-curable acrylic latex dispersion
formed by making a two stage polymer of overall composition 40 wt %
BA/32 wt % MMA/25 wt % MAA/3.0 wt % ALMA using the process
described in Example 1. 15% of the acid equivalents are neutralized
with ammonium hydroxide. To this composition is added an amount of
glycidyl methacrylate corresponding to 74 mole percent of the acid,
and reacting at 80.degree. C. until essentially all the glycidyl
methacrylate has reacted.
[0086] Latex B produced by the foregoing procedure will be a
radiation curable latex binder blend, in accordance with the
present invention, that is suitable for formulating into a
radiation curable aqueous ink jet ink composition. Latex B should
have approximately 15 wt % solids content, based on the total
weight of Latex B. In the event that the solids content of Latex B
is greater than the desired 15 wt %, water or another suitable
aqueous medium is added and mixed therewith to attain the desired
15 wt %. More particularly, the solids component of Latex B
includes a radiation curable, dispersible polymer binder
composition that contains functionalities in the form of
methacrylate functionalities which are available for initiation
upon exposure to UV radiation. The radiation curable, dispersible
polymer binder composition is expected to have a molecular weight
of from about 500,000 to about 2,500,000.
Example 3 (Comparative)
Unreactive Latex Binder Blend--Not Crosslinked
[0087] Comparative Latex C is an unreactive latex dispersion formed
by preparing a two stage polymer of overall composition 60 wt %
BA/35 wt % MMA/5 wt % MAA, using the process described in Example
1. The resulting Latex C has no residual methacrylate functionality
and is, therefore unreactive when exposed to actinic radiation. It
is neutralized with ammonia to pH 7.0. The resulting Latex C is not
expected to be effective as a radiation curable polymer binder
blend for formulation into radiation curable latex ink jet ink
compositions.
Example 4 (Comparative)
Unreactive Latex Binder Blend--Crosslinked
[0088] Comparative Latex D is an unreactive latex dispersion formed
by preparing a polymer of composition 40 wt % BA/35 wt % MMA/21 wt
% EA/3 wt % ALMA/1 wt % MAA using the process described in Example
1. The resulting Latex D is not expected to be effective as a
radiation curable polymer binder blend for fomulation into curable
latex ink compositions
Example 5
Acrylic-Urethane Radiation Curable Latex Binder Blend for Radiation
Curable Aqueous Ink Jet Ink Composition
[0089] Latex E is prepared by adding 10 g of CN-981 (urethane
acrylate oligomer available from Sartomer Company, USA) to 100 g of
Latex B, described hereinabove in Example 2. The mixture is mixed
for 1 hour.
[0090] The resulting Latex E produced by the foregoing procedure
will be a radiation curable latex binder blend, in accordance with
the present invention, that is suitable for formulating into a
radiation curable latex ink jet ink composition. Latex E should
have approximately 15 wt % solids content, based on the total
weight of Latex E and water or another suitable aqueous medium
should be added and mixed therewith in the event that the solids
content is initially higher than the desired 15 wt %. The solids
component of Latex F includes radiation curable, dispersible
polymer binder compositions that contain functionalities in the
form of epoxy and acrylate functionalities which are available for
initiation upon exposure to UV radiation. The radiation curable,
dispersible polymer binder compositions are expected to have a
molecular weight of from about 500,000to about 2,500,000.
Example 6
Radiation Curable Acrylic Latex Binder Blend for Radiation Curable
Aqueous Ink Jet Ink Composition
[0091] Latex F is a radiation-curable acrylic latex dispersion
formed by making a polymer of overall composition 20 wt % FMA/20 wt
% BA/35 wt % MMA/13 wt % MAA/2 wt % ALMA/10 wt % TMPTA using the
process described for Latex A. 15% of the acid equivalents are
neutralized with ammonium hydroxide. To this composition is added
an amount of glycidyl methacrylate corresponding to 74 mole percent
of the acid, and reacting at about 80.degree. C. until essentially
all the glycidyl methacrylate has reacted.
[0092] Latex F produced by the foregoing procedure will be a
radiation curable latex binder, in accordance with the present
invention, that is suitable for formulating into a radiation
curable latex ink jet ink composition. Latex F should have
approximately 15 wt % solids content, based on the total weight of
Latex F, and water or another suitable aqueous medium should be
added and mixed therewith in the event that the solids content is
initially higher than the desired 15 wt %. More particularly, the
solids component of Latex F includes a radiation curable polymer
binder composition that contains functionalities in the form of
methacrylate functionalities which are available for initiation
upon exposure to UV radiation. The radiation curable, dispersible
polymer binder composition is expected to have a molecular weight
of from about 500,000 to about 2,500,000.
Example 7
Crosslinked Curable Acrylic Latex Binder for Curable Aqueous Ink
Jet Ink Composition
[0093] Latex G is a radiation-curable acrylic latex dispersion
formed by making a polymer of overall composition 20 wt % TBAEMA/20
wt % BA/35 wt % MMA/20 wt % HEMA/5 wt % ALMA using the process
described in Example 1. To this composition is added an amount of
glycidyl methacrylate corresponding to 74 mole percent of the
amine, and reacting at about 80.degree. C. until essentially all
the glycidyl methacrylate has reacted.
[0094] Latex G produced by the foregoing procedure will be a
radiation curable latex binder blend, in accordance with the
present invention, that is suitable for formulating into a
radiation curable latex ink jet ink composition. Water or another
suitable aqueous medium should be added and mixed therewith in the
event that the solids content is initially higher than the desired
15 wt %. The solids component of Latex G includes a radiation
curable, dispersible polymer binder composition that contains
functionalities in the form of methacrylate functionalities which
are available for initiation upon exposure to UV radiation. The
radiation curable, dispersible polymer binder composition is
expected to have a molecular weight of from about 500,000 to about
2,500,000.
Example 8
Rubber Core/Shell Radiation Curable Latex Binder Blend for
Radiation Curable Aqueous Ink Jet Ink Composition
[0095] Latex H is a radiation-curable core/shell acrylic latex
dispersion formed by the following process.
[0096] A core/shell emulsion polymer is prepared, by a well known
process, with a first stage composition of 84 wt % BA/10 wt % DVB/5
wt % ALMA/1 wt % MAA and a second stage composition of 60 wt %
EA/24 wt % styrene/1 wt % MAA/10 wt % DVB/5 wt % ALMA. The weight
ratio of first stage monomer to second stage monomer in this
core/shell polymer is 1 to 1.
Preparation of Stage One Monomer Emulsion
[0097] 84 g of BA, 10 g of DVB, 5 g of ALMA and 1 g of MAA are
premixed in a small container. Charge 1.5 g of SLS (28%) and 100 g
of water into a separate monomer emulsion container. The premix
monomer is added into the monomer emulsion container under
agitation over 30 minutes to form the stage one monomer
emulsion.
Preparation of Stage Two Monomer Emulsion
[0098] 60 g of EA, 24 g of styrene, 1 g of MAA, 10 g of DVB and 5 g
of ALMA are premixed in a small container. Charge 1.5 g of SLS
(28%) and 100 g of water into a separate second monomer emulsion
container. The premix monomer is added into the second monomer
emulsion tank under agitation over 30 minutes to form the stage two
monomer emulsion.
Polymerization of Stage One and Stage Two Monomers
[0099] A reactor is charged 200 g of water and 9.0 g of SLS (28%)
under agitiation. The reactor and its contents are heated to
85.degree. C. At 85.degree. C., 30 g of the stage one monomer
emulsion above is charged into the reactor along with a mixture of
0.4 g of ammonium persulfate in 10 g of water and the mixture is
allowed to stand for 10 minutes. The rest of the stage one monomer
emulsion is charged into the reactor over a period of 60 minutes
along with a co-feed initiator solution prepared from 0.1 g of
ammonium persulfates in 10 g of water. The co-feed initiator
solution is also fed into the reactor over a period of 60 minutes.
The stage two monomer emulsion is fed to the reactor as soon the
first stage monomer emulsion feed ends. The stage two monomer
emulsion is charged into the reactor over a period of 60 minutes,
along with a co-feed initiator solution prepared from 0.1 g of
ammonium persulfate in 10 g of water. The co-feed initiator
solution is also fed into the reactor over a period of 60 minutes.
The reactor is then cooled to 55.degree. C. Aqueous solutions 1 g
of t-butyl hydroperoxide (70%) in 5 g of water and 0.5 g of sodium
formaldehyde sulfoxylate in 10 g of water are added sequentially
with 20-minute hold periods at 55.degree. C.
[0100] Latex H produced by the foregoing procedure will be a
radiation curable latex binder blend, in accordance with the
present invention, that is suitable for formulating into a
radiation curable latex ink jet ink composition. Latex H should
have approximately 15 wt % solids content, based on the total
weight of Latex H, and water or another suitable aqueous medium
should be added and mixed therewith in the event that the solids
content is initially higher than the desired 15 wt %. More
particularly, the solids component of Latex H includes a radiation
curable, dispersible polymer binder composition that contains
radiation curable functionalities which are available for
initiation upon exposure to UV radiation. The radiation curable,
insoluble polymer binder composition is expected to have a
molecular weight of from about 500,000 to about 2,500,000.
Radiation Curable Aqueous Ink Jet Ink Compositions
[0101] The radiation curable latex binder blends, which include the
radiation curable, dispersible polymer binder compositions of the
present invention, can be formulated into radiation curable latex
ink jet ink compositions capable of application to susbtrates by
ink jet technologies.
[0102] More particularly, the radiation curable latex binder blends
described in Examples 1 through 8 can be formulated into cyan ink
jet inks according to the combination of ingredients as shown in
Table 1 below. Examples of eight individual radiation curable latex
ink jet ink compositions (i.e., Inks A through H) in accordance
with the present invention are provided, i.e., one ink composition
for each latex binder blend of Examples 1 through 8 (including
comparative Examples 3 and 4). It is noted that the numberic values
in Table 1 are weight percents based upon the total weight of each
ink composition.
1TABLE 1 Sample Radiation Curable Latex Ink Jet Ink Compositions
(for UV Curable Inks) Ink C Ink D Composition Ink A Ink B
Comparative Comparative Ink E Ink F Ink G Ink H AcryJet .TM. Cyan
157 17.50 17.50 17.50 17.50 17.50 17.50 17.50 17.50 Latex A 25.00
Latex B 25.00 Latex C (comparative) 25.00 Latex D (comparative)
25.00 Latex E 25.00 Latex F 25.00 Latex G 25.00 Latex H 25.00
Ammonium nitrate 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 (25% in
Water) N-methylpyrrolidone 6.50 6.50 6.50 6.50 6.50 6.50 6.50 6.50
Liponic EG-7 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Dynol 604 0.50
0.50 0.50 0.50 0.50 0.50 0.50 0.50 1,3-propanediol 10.20 10.20
10.20 10.20 10.20 10.20 10.20 10.20 DI water 31.30 31.30 36.30
36.30 31.30 31.30 31.30 31.30 Esacure .TM. DP 250 5.0 5.0 -- -- 5.0
5.0 5.0 5.0 AcryJet .TM. is a trademark of the Rohm and Haas
Company, Philadelphia, PA, U.S.A. The ammonium nitrate serves as a
pH buffer and N-methylpyrrolidone functions as a penetrant in the
curable latex ink compositions. Liponic EG-7 is a humectant which
is available from Lipo Chemicals, Inc. Dynol 604 is a surfactant
available from Air Products company, U.S.A. 1,3-propanediol
functions as a humectant and/or penetrant. Esacure DP 250 is a
water dispersible photoinitiator available from Lamberti S. p. A.,
Italy.
[0103] Examples of E-beam radiation curable latex ink jet ink
compositions which incorporate Latexes A, B, C, F and G are
provided in Table 2 below. It is noted that, as is well known in
the art, E-beam radiation curable ink jet ink compositions do not
require the inclusion of photoinitiators. Thus, for comparison,
selected radiation curable latex ink jet ink compositions (i.e.,
Inks A, B, C, F and G) from Table 1 above have been modified by
elimination of the photoinitiator and adjustment of the amounts of
the remaining components of the ink composition.
2TABLE 2 Sample Radiation Curable Latex Ink Jet Ink Compositions
(for E-beam Curable Inks) Ink C' Composition Ink A' Ink B'
Comparative Ink F' Ink G' AcryJet .TM. Cyan 157 17.50 17.50 17.50
17.50 17.50 Latex A 25.00 Latex B 25.00 Latex C (comparative) 25.00
Latex G 25.00 Latex H 25.00 Ammonium nitrate 3.00 3.00 3.00 3.00
3.00 (25% in Water) N-methylpyrrolidone 6.50 6.50 6.50 6.50 6.50
Liponic EG-7 1.00 1.00 1.00 1.00 1.00 Dynol 604 0.50 0.50 0.50 0.50
0.50 1,3-propanediol 10.20 10.20 10.20 10.20 10.20 DI water 36.30
36.30 36.30 36.30 36.30
[0104] For all of the curable latex ink compositions provided in
Tables 1 and 2, after the final ink jet ink compositions are
formulated and well-mixed, they are each filtered using a 1 micron
filter. Each ink jet ink composition shown in Tables 1 and 2 would
be applied separately to a substrate. Each ink composition would
then be cured under either a UV lamp or an electron beam lamp, as
appropriate to the nature of the particular ink, to initiate
reaction of the photocurable functionalities of the latex binder
blends (also known as "curing", which results in further
crosslinking).
[0105] The UV curable latex ink jet ink compositions labeled Ink A,
Ink B and Inks E through H (which contain Latexes A, B and E
through H, respectively) are expected to demonstrate improvements
in one or more of the following properties over the comparative
latex ink compositions labeled Ink C and Ink D (which contain
comparative Latexes C and D, respectively), when applied and cured
onto a substrate: durability, crock resistance, color retention,
smear resistance, water resistance, optical density, image quality
and lightfastness.
[0106] With reference to the E-beam curable latex ink compositions
of Table 2, it is expected that the radiation curable latex ink jet
ink compositions labeled Ink A', Ink B', Ink G' and Ink H' are
expected to show improved properties, compared to Ink C', in one or
more of the following properties when applied and cured onto a
substrate: Jettability, durability, crock resistance, color
retention, smear resistance, water resistance, optical density,
image quality, hold out and lightfastness.
* * * * *